Experiments have been performed on microglia, the resident macrophage in the central nervous system cultured from cerebral cortices of normal and trisomy 16 (Tsl6) mice. The Tsl6 mouse serves as an animal model of humans afflicted with Down's syndrome (trisomy 2l). We found that interferon (alfa IFN), a cytokine, increases the sensitivity of phorbol myristate acetate (PMA) on microglial production of the superoxide radical anion and that IFN also increases the production of interleukin-1 (IL-1), another cytokine. The increase in production of IL-1 is larger for the Ts16 mouse than for normal controls.